Climate Prediction Center

US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT MAY 09 2008

SYNOPSIS: AN ACTIVE WEATHER PATTERN IS EXPECTED FOR THIS ASSESSMENT PERIOD. A STRONG SURFACE LOW PRESSURE SYSTEM WILL MOVE OFF THE NORTHEAST/MIDDLE ATLANTIC COAST EARLY IN THE PERIOD, WHICH MAY BRING HEAVY RAIN TO PORTIONS OF THE MIDDLE ATLANTIC. HIGH WINDS ALONG THE NORTHEAST/MIDDLE ATLANTIC COAST WILL LIKELY ACCOMPANY THIS STORM SYSTEM. THESE HIGH WINDS AND STRONG LOW PRESSURE COULD LEAD TO STORM SURGE, COASTAL FLOODING, AND BEACH EROSION. UPSTREAM OF THIS STORM SYSTEM, ANOTHER LOW PRESSURE IS EXPECTED TO FORM OVER THE CENTRAL PLAINS AND MOVE EASTWARD THROUGH THE CONUS. THIS WILL BRING A BROAD SWATH OF RAIN TO THE EASTERN TWO THIRDS OF THE CONUS. A LOW PRESSURE SYSTEM WILL MOVE INTO WESTERN ALASKA FROM THE BERING SEA, WHICH WILL BRING RAIN AND POSSIBLY HIGH WINDS TO COASTAL REGIONS EARLY IN THE PERIOD. ANOTHER STRONG LOW PRESSURE SYSTEM WILL REACH ALASKA BY MAY 14, WHICH WILL LIKELY BRING HIGH WINDS AND HEAVY RAIN TO THE SOUTHERN COAST OF ALASKA.

HAZARDS

HEAVY RAIN OVER PARTS OF THE MIDDLE ATLANTIC MAY 12.
HIGH WINDS OVER THE MIDDLE ATLANTIC AND NORTHEAST COAST MAY 12-MAY 13.
HEAVY RAIN OVER PARTS OF THE SOUTHERN COAST OF ALASKA MAY 15.
HIGH WINDS ACROSS THE SOUTHERN COAST OF ALASKA MAY 12, AND MAY 14-MAY 15.
ONGOING LOCALIZED RIVER FLOODING OVER THE MIDDLE AND LOWER MISSISSIPPI VALLEY.
ENHANCED RISK OF WILDFIRE ACROSS PORTIONS OF THE SOUTHWEST, SOUTHERN PLAINS, AND COLORADO MAY 12.
ELEVATED WILDFIRE RISK ACROSS PARTS OF NEW MEXICO AND TEXAS MAY 13.
SEVERE DROUGHT PERSISTS IN PARTS OF THE PLAINS, WESTERN US, WITH SOME RELIEF POSSIBLE IN THE SOUTHEAST.

DETAILED SUMMARY

FOR MONDAY MAY 12 - WEDNESDAY MAY 14: A SURFACE LOW PRESSURE SYSTEM WILL MOVE OFF THE NORTHEAST/MIDDLE ATLANTIC COAST EARLY IN THE PERIOD, BRINGING HEAVY RAIN TO PARTS OF THE MIDDLE ATLANTIC. THERE WILL ALSO BE HIGH WINDS AFFECTING THE NORTHEAST/MIDDLE ATLANTIC COAST DUE TO THE EXPECTED STRONG PRESSURE GRADIENT. THESE HIGH WINDS AND DEEP LOW PRESSURE WILL LIKELY LEAD TO STORM SURGE, COASTAL FLOODING AND BEACH EROSION IN THE AFFECTED AREA. AS THIS SURFACE LOW MOVES OFF THE COAST, AN UPPER LEVEL SHORTWAVE IS EXPECTED TO MOVE EASTWARD INTO THE CONUS FROM THE PACIFIC NORTHWEST. THERE ARE DIFFERENCES CONCERNING THE SPEED OF THE MOVEMENT OF THE UPPER LEVEL TROUGH, WITH THE 0Z EUROPEAN BEING MUCH MORE PROGRESSIVE THAN THE 6Z GFS. DESPITE THESE DIFFERENCES, THERE WILL BE FAVORABLE WIND CONDITIONS AND LOW RELATIVE HUMIDITIES WHICH WILL ENHANCE THE RISK OF WILDFIRES ACROSS PORTIONS OF THE SOUTHWEST, SOUTHERN PLAINS, AND COLORADO MAY 12 AND ACROSS PARTS OF NEW MEXICO AND TEXAS MAY 13. AHEAD OF THIS SHORTWAVE A SURFACE LOW PRESSURE WILL DEVELOP OVER THE CENTRAL PLAINS AND MOVE EASTWARD. THIS LOW PRESSURE SYSTEM WILL LIKELY BRING RAIN TO THE EASTERN TWO THIRDS OF THE CONUS, WHICH WILL CONTINUE THE THREAT FOR LOCALIZED RIVER FLOODING ACROSS THE MIDDLE AND LOWER MISSISSIPPI VALLEY. SEVERE DROUGHT PERSISTS IN PARTS OF THE PLAINS, WESTERN US, WITH SOME RELIEF POSSIBLE IN THE SOUTHEAST. A SURFACE LOW PRESSURE SYSTEM IS ANTICIPATED TO APPROACH WESTERN ALASKA FROM THE BERING SEA, WHICH MAY BRING HIGH WINDS TO THE SOUTHERN COAST OF ALASKA MAY 12. ANOTHER STRONG SURFACE LOW PRESSURE EXPECTED TO MIGRATE INTO ALASKA FROM THE GULF OF ALASKA. ASSOCIATED WITH THIS DEEP SURFACE LOW, HIGH WINDS ARE EXPECTED ACROSS THE SOUTHERN COAST OF ALASKA.

FOR THURSDAY MAY 15 - MONDAY MAY 19: THE SOUTHERN COAST OF ALASKA WILL EXPERIENCE HIGH WINDS AS WELL AS HEAVY RAIN DUE TO THE DEEP SURFACE LOW PRESSURE SYSTEM EARLY IN THE PERIOD. THERE IS MODEL AGREEMENT FOR AN AMPLIFIED UPPER LEVEL TROUGH TO BE SITUATED OVER THE CENTRAL CONUS EARLY IN THIS PERIOD AND PROPAGATING EASTWARD. MODELS SHOW GREAT DISCREPENCIES CONCERNING THE EVOLUTION OF THIS TROUGH. THE 0Z EUROPEAN MOVES EASTWARD FASTER THAN THE 6Z GFS AND FORMS A CUTOFF LOW OVER THE GREAT LAKES, WHEREAS THE 6Z GFS MOVES THE TROUGH SLOWER. THE 0Z EUROPEAN, UNLIKE THE 0Z GFS ALSO SPLITS SOME ENERGY TOWARDS THE SOUTHWEST INTO A CUTOFF LOW. OVERALL, THERE IS GOOD MODEL CONSENSUS FOR AN UPPER LEVEL PATTERN OF AMPLIFIED TROUGHING OVER THE EASTERN TWO THIRDS OF THE CONUS AND RIDGING OVER THE WESTERN THIRD OF THE CONUS. WETTER THAN NORMAL CONDITIONS ARE FORECAST FOR THE EASTERN THIRD OF THE COUNTRY AND SOUTHWESTERN ALASKA, WHILE DRIER THAN NORMAL CONDITIONS ARE EXPECTED FOR THE WESTERN TWO THIRDS OF THE CONUS, NORTHWESTERN ALASKA, AND THE ALEUTIANS. BELOW NORMAL TEMPERATURES ARE EXPECTED FOR THE EASTERN TWO THIRDS OF THE CONUS AND THE NORTHERN AND SOUTHERN COASTS OF ALASKA. THE WESTERN THIRD OF THE CONUS AND THE SOUTHERN TIP OF FLORIDA IS FORECAST TO HAVE ABOVE NORMAL TEMPERATURES.

FOR TUESDAY MAY 20 - FRIDAY MAY 23: THE 6Z GFS DEPICTS AN UPPER LEVEL TROUGH DEVELOPING OVER THE NORTHERN PLAINS AND MOVING EASTWARD OVER THIS TIME PERIOD, WHICH COULD BRING RAIN TO THE EASTERN TWO THIRDS OF THE CONUS. THERE IS ALSO THE POSSIBILITY FOR A CUTOFF LOW TO MOVE INTO ALASKA FROM THE GULF OF ALASKA. DUE TO THE INHERENT UNCERTAINTY OF MODELS FOR THIS TIME RANGE, NO HAZARDS CAN BE MADE FOR THIS PERIOD.

FORECASTER: MELISSA OU

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